1.4 Multiply whole numbers

Use multiplication notation

Suppose you were asked to count all these pennies shown in [link] .

Would you count the pennies individually? Or would you count the number of pennies in each row and add that number $3$ times.

Multiplication is a way to represent repeated addition. So instead of adding $8$ three times, we could write a multiplication expression.

We call each number being multiplied a factor and the result the product    . We read $3\times 8$ as three times eight , and the result as the product of three and eight .

There are several symbols that represent multiplication. These include the symbol $\times$ as well as the dot, $·$ , and parentheses $(\text{).}$

Model multiplication of whole numbers

There are many ways to model multiplication. Unlike in the previous sections where we used $\text{base-10}$ blocks, here we will use counters to help us understand the meaning of multiplication. A counter is any object that can be used for counting. We will use round blue counters.

Multiply whole numbers

In order to multiply without using models, you need to know all the one digit multiplication facts. Make sure you know them fluently before proceeding in this section.

[link] shows the multiplication facts. Each box shows the product of the number down the left column and the number across the top row. If you are unsure about a product, model it. It is important that you memorize any number facts you do not already know so you will be ready to multiply larger numbers.